jdbc学习

JDBC查询技巧：多条件的查询，将查询条件放入List<Map>中

public List<Book> query(List<Map<String, Object>> params)throws SQLException {Connection conn = UDtest1.getConn();List<Book> books = new ArrayList<Book>();StringBuilder sb = new StringBuilder();sb.append("select * from Book where 1=1");//注意这里1=1在构建sql语句时会经常用到，小技巧if(params!=null && params.size()>0){for(int i=0;i<params.size();i++){Map<String, Object> map=params.get(i);//取出每个表达式，加到sql语句后面sb.append(" and "+map.get("name")+" "+map.get("rela")+" "+map.get("value")+" ");}}PreparedStatement ps=conn.prepareStatement(sb.toString());ResultSet rs = ps.executeQuery();Book book = null;while (rs.next()) {book = new Book();book.setID(rs.getInt("ID"));book.setBookNum(rs.getString("bookNum"));book.setBookName(rs.getString("bookName"));book.setBookConcern(rs.getString("bookConcern"));book.setBookAuthor(rs.getNString("bookAuthor"));book.setBookCount(rs.getString("bookCount"));book.setBookPrice(rs.getString("bookPrice"));books.add(book);}return books;}